The O-transfer reaction, a possible link between the organic chemistry of singlet oxygen and ozone, will be examined with O18 as a tracer in the reaction of a hindered olefin with singlet oxygen, generated both by photosensitization and by thermal phosphite ozonide route, which we have developed into a precise method applicable over a range of temperatures. A subsidiary objective of this program is to develop a method of detecting singlet oxygen and ozone in each other's presence. The unique properties of liquid carbon dioxide as a solvent will be further examined; the unknown compounds alpha-acetolactone and dihalo-alpha-acetolactones are expected to be available from carbene reactions in this solvent, to be more resistant to spontaneous polymerization than the known diphenyl-alpha-acetolactone, and possibly to be available for interesting new perspectives on the physiological properties of active alkylating agents.